Dust suppression formulas using plasticized cellulose ethers

ABSTRACT

A method of treating a plurality of fines of a dusting material to prevent emanation of dust from the dusting material is described. An aqueous solution comprising a mixture of soluble non-ionic cellulose ether, a plasticizer, and a surfactant is provided. The aqueous solution is applied to a dusting material comprising a plurality of fines. The dusting material is transferred during the applying step from a first location to a second location as the aqueous solution is applied to the plurality of fines. The dusting material is mixed with the aqueous solution to coat the plurality of fines with the aqueous solution. The treated dusting material is accumulated into a mass of the material subsequent to the applying step wherein the aqueous solution is substantially evenly distributed throughout an interior portion of the mass of the treated dusting material.

CROSS-REFERENCE TO RELATED APPLICATIONS

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FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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TECHNICAL FIELD

The invention relates to suppression of dust; more particularly, thepresent invention relates to an unexpectedly effective aqueous solutionof a soluble cellulose ether, a plasticizer, and one or more surfactantsand mixing a dusting material with the aqueous solution, therebyreducing or eliminating the ability of the dusting material to generatedust during routine handling.

BACKGROUND OF THE INVENTION

The generation of dust during transport and handling of material haslong been recognized as an economic loss and a health hazard. In generalthere are four ways to prevent dust generation using a chemicalsolution. Two are temporary: using foam to form a physical blanket overthe material, usually when it is on a conveyor belt, or usingsurfactants in water to wet the dusting material and prevent dustgeneration through multiple handling points. These remedies last only aslong as the foam remains intact or the material remains wet. The secondtwo approaches focus on longer-term dust control. They involve applyinga chemical binder to the surface of a stock pile or railcar to form acrust, preventing wind-born loss, or to treat the entire mass ofmaterial with a binder, cementing the smaller dust particles to largerparticles on a semi-permanent basis. The former approach, depending onthe choice of binder, can form a crust lasting over a year. The latter,depending on the choice of binder, can render a dusting materialeffectively non-dusting for a time ranging from days to months. Wereport here an improvement of the latter technology.

There have been any number of compositions put forth over many decadesto address this. Most of these center around handling coal. As early as1931, Wallace (U.S. Pat. No. 1,910,975) taught the application ofhygroscopic sugary materials such as molasses to prevent dusting incoal. Of greater note is Work et. al.'s (U.S. Pat. No. 2,250,287) 1940recognition that a “ . . . strong, abrasion-resistant coating . . . ”was preferred as a dust-proofing agent for coal. While the use ofcalcium chloride and other hygroscopic salts to retain moisture on coalhad been previously taught, in 1943 Kleinicke et al. (U.S. Pat. No.2,436,146) added organic gels such as starch, gelatin, or agar toenhance the performance of these salts. More recently, Trechock et al.(U.S. Pat. No. 3,711,318) taught the use of film-forming compositionsincluding sodium silicate, asphalt, coal tar, and molasses tosubstantially reduce <325 mesh dust production on coke briquettes. In1974, Salyer et al. (U.S. Pat. No. 3,954,662) taught the use ofcopolymers of vinyl esters and unsaturated dicarboxylic acids andanhydrides with wetting agents to suppress dust on coal. Beck et al.(U.S. Pat. No. 4,055,471) reported the use of waste sulfite liquor(lignosulfonates) to suppress dust on coal before feeding it to a cokingoven. It is worth noting that at about this time, Callahan et al. (U.S.Pat. No. 4,369,121) reported the use of water-soluble nonionic celluloseethers to form a pile seal over the surface of stockpiles, however hedid not teach the use of this composition as a dust-proofing agent fortreating the bulk of the aggregate, nor did his composition contain aplasticizer. Shimizu et al. (U.S. Pat. No. 4,428,984) later taught theuse of a polyhydridic alcohol; preferably glycerin, and a wetting agentas a dust-reducing treatment. Fenton (U.S. Pat. No. 4,469,612) taughtthe use of polyacrylates and copolymers of acrylics as dustagglomerating agents specifically for use with oil-shale derived fines.Kittle (U.S. Pat. No. 4,561,905) taught the use of foamed heavy processoil to suppress coal dust. At almost the same time, Siddoway et al.(U.S. Pat. No. 4,582,511) taught the use of sugar or molasses as a bodytreatment top suppress coal dust. Yan's (U.S. Pat. No. 4,462,196) use ofa gelatinized starch illustrates yet another possible composition forsuppressing coal dust. Roberts et al. (U.S. Pat. No. 4,650,598) taughtthe advantage of adding a small amount of a polyacrylate orpolymethacrylate to kerosene in an oil in water emulsion for dustcontrol on coal. This is very similar to Roe's (U.S. Pat. No. 4,780,233)teaching of using polyisobyutlyene to enhance the effectiveness of oilin an oil in water emulsion for dust control. The two previous patentstaught the use of kerosene or mineral-based oils and this contrasts withZinkan's (U.S. Pat. No. 4,801,635) approach of using anionic andnonionic water soluble (non-cellulosic) polymers with a wetting agent.Returning to petroleum-based compositions, Wajer et al. (U.S. Pat. No.5,192,337) taught the use of petroleum resin diluted with mineral oil toreduce dusting on coal. Roe et al. (U.S. Pat. No. 5,194,174), at roughlythe same time, taught the use of polyvinyl alcohol with cross-linkers,wetting agents, and plasticizers for dust control. Of particular note isthe work of Winstanley et al. (U.S. Pat. No. 5,223,165), which teachesthe use of alkyl glycosides for dust control. While the alkyl glycosidesare wetting agents and the focus of the patent, the use of hydrophilicbinders including cellulose derivatives in combination with the wettingagents is taught. Again, nowhere is there any mention of the use of aplasticizer to enhance dust suppression. Roe (U.S. Pat. No. 5,271,859)discussed dust control methods at high temperature; that is, greaterthan 250° F., using nonionic cellulose ethers. There are additionalpatents covering the use of a variety of binders to render materials nondusting. Included in that list would be teachings related to the use ofcationic polymers (Roe, U.S. Pat. No. 5,256,444); lignosulfonate plusadditives (Bennet, U.S. Pat. No. 5,310,494; U.S. Pat. No. 5,578,239);hydrated grain endosperm (Rogers et al., U.S. Pat. No. 5,658,486);distillation bottoms from 1,6-hexanediol production (McNabb et al., U.S.Pat. No. 5,820,787); and molasses and oil or simply molasses protein(Rahm et al., U.S. Pat. No. 6,086,647; Wolff et al., U.S. Pat. No.6,790,245).

From the references set forth above, it is apparent that there are avariety of options available to render a material non-dusting. Howeverthe majority of the above treatments rely on a strong binder to performtheir function. As was taught by Work et al. in 1940, strength isessential as it relates to the basic mechanism by which dust issuppressed. Dust is suppressed when a composition binds the looseparticles of the bulk material together. The stronger the bond betweenthe bulk material particles, the less likely dust will separate from thesubstrate on mechanical agitation.

Of note to this disclosure is Roe's (U.S. Pat. No. 5,271,859) teachingof the use of water-soluble cellulose ethers with an additional wettingagent or plasticizer at temperatures above 250° F. as a dust palliative.In particular, Roe's claimed invention specifically calls for theaddition of either a plasticizer or a wetting agent but not both.

Water-soluble cellulose ethers are well-known in the coatings industry.Their behavior with plasticizers has been studied extensively. As longago as 1940 it was recognized that the addition of a plasticizerweakened the tensile strength of cellulose ether films (Kropscott, U.S.Pat. No. 2,226,823). Oakley (U.S. Pat. No. 2,653,108) made a similarobservation. More recently Part et al. (Park, H. J., Weller, C. L.,Vergano, P. J., and Testin, R. F.; Journal of Food Science, 58, #6, 1993pp 1361-1364) quantified the same behavior specifically in methylcellulose and hydroxypropyl methyl cellulose using, among otherplasticizers, propylene glycol and glycerin (2,3-hydroxy-1-propanol). ADOW Corporation website discusses not only strength, but film toughnessand Young's Modulus(http://dowwolff.custhelp.com/app/answers/detail/a_id/2357/˜/methocel-effect-of-plasticizers-on-film-properties-in-tablet-coatings).In every case the addition of glycerin or propylene glycol weakened thefilms. It is therefore a surprising and unexpected result that theaddition of a plasticizer to dust control formulas similar to thosedescribed by Roe would result in improved strength.

The present invention is provided to solve the problems discussed aboveand other problems, and to provide advantages and aspects not providedby prior dust suppression fluids of this type. A full discussion of thefeatures and advantages of the present invention is deferred to thefollowing detailed description, which proceeds with reference to theaccompanying drawings.

SUMMARY OF THE INVENTION

An aspect of the present invention is directed to method of reducingairborne dust emanating from a plurality of fines of a dusting material.The method comprises the steps of (1) providing a source of an aqueoussolution comprising a mixture of water soluble cellulose ether, aplasticizer, and one or more surfactants; (2) applying the aqueoussolution to a dusting material comprising a plurality of fines to createa treated dusting material; and (3) mixing the dusting material with theaqueous solution to coat the plurality of fines with the aqueoussolution. The method may further comprise the steps of (1) transferringthe dusting material during the applying step wherein the dustingmaterial is being transferred from a first location to a second locationas the aqueous solution is applied to the plurality of fines, and/or (2)accumulating the plurality of fines of the treated dusting material intoa mass of the dusting material subsequent to the applying step whereinthe aqueous solution is substantially evenly distributed throughout aninterior portion of the mass of the treated dusting material. The mixingstep can be performed simultaneously with the accumulating step.

The aqueous solution may have the following properties. The solublecellulose ether may be a non-ionic cellulose ether, and the plasticizermay be glycerin. The non-ionic cellulose ether may have a viscositybetween 3 cPs and 100,000 cPs as measured at a concentration of 2.5percent in water. The non-ionic cellulose ether may be a hydroxypropylmethylcellulose ether. A percentage of the non-ionic cellulose ether isno more than 20 percent by weight of the aqueous solution. A percentageof the plasticizer in the aqueous solution may be no more than 200percent weight of the non-ionic cellulose ether.

Another aspect of the present invention is directed to a method oftreating a plurality of fines of a dusting material to prevent emanationof dust from the dusting material. This method comprises the steps of(1) providing an aqueous solution comprising a mixture of solublenon-ionic cellulose ether, a plasticizer, and a surfactant; (2) applyingthe aqueous solution to a dusting material comprising a plurality offines to create a treated dusting material; and (3) accumulating theplurality of fines of the dusting material into a mass of the dustingmaterial subsequent to the applying step wherein the aqueous solution issubstantially evenly distributed throughout an interior portion of themass of the dusting material. The method may further comprise the stepsof (1) mixing the dusting material with the aqueous solution to coat theplurality of fines with the aqueous solution, and or (2) transferringthe dusting material during the applying step wherein the dustingmaterial is transferred from a first location to a second location asthe aqueous solution is applied to the plurality of fines.

The aqueous solution may have one or more of the following properties,alone or in any reasonable combination. The non-ionic cellulose ether isan alkyl-substituted cellulose ether. The plasticizer may be selectedfrom a group of cellulose ether plasticizers consisting of polyols,diols, sugars, fatty acids, fatty acid esters, and polyhydridicalcohols. The plasticizer may be selected from a group consisting ofdiethylene glycol, propylene glycol, glycerin, triethanolamine,dextrose, and pentaerythritol. The surfactant may be selected from thegroup consisting of surfactants known to be effective on the dustingmaterial to be treated. The non-ionic cellulose ether may be is at leasta partially substituted hydroxy-alkyl cellulose ether. The hydroxy-alkylcellulose ether may be hydroxypropyl cellulose ether or hydroxyethylcellulose ether. The plasticizer may be selected from a group of knowncellulose ether plasticizers. The plasticizer may be selected from thegroup consisting of alkylene glycols, dialkylene glycols, sugars, andglycerin. The plasticizer may be selected from the group consisting ofpropylene glycol, diethylene glycol, and glycerin. The surfactant may beselected from the group consisting of solutions of salts of alkylbenzenesulfonates, dialkyl sulfosuccinates, fatty acid amides, quaternaryammonium compounds, organic phosphate esters, ethylene oxide-propyleneoxide block copolymers, nonionic fatty acid alcohol ethoxylates,nonionic fatty acid alcohol mixed ethoxylate-propoxylates, syntheticalcohol ethoxylates, and synthetic alcohol mixedethoxylate-propoxylates. The surfactant may be selected from the groupconsisting of solutions of salts of alkylbenzene sulfonates, dialkylsulfosuccinates, nonionic fatty acid alcohol ethoxylates, and syntheticalcohol ethoxylates. A cross-linking agent may be added to theformulation. The cross-linking agent may be glyoxal or glutaraldehyde

Another aspect of the present invention is directed to a method oftreating a plurality of fines of a dusting material to prevent emanationof dust from the dusting material. The method comprises the steps of:(1) providing an aqueous solution comprising a mixture of solublenon-ionic cellulose ether, a plasticizer, and a surfactant; (2) applyingthe aqueous solution to a dusting material comprising a plurality offines to create a treated dusting material; (3) transferring the dustingmaterial during the applying step wherein the dusting material istransferred from a first location to a second location as the aqueoussolution is applied to the plurality of fines; (4) mixing the dustingmaterial with the aqueous solution to coat the plurality of fines withthe aqueous solution; and (5) accumulating the plurality of fines of thetreated dusting material into a mass of the treated dusting materialsubsequent to the applying step wherein the aqueous solution issubstantially evenly distributed throughout an interior portion of themass of the treated dusting material.

The aspects of the invention described above include use of non-ioniccellulose ether solutions with a plasticizer and surfactant to reduce oreliminate the ability of a dusting material to generate dust forextended periods of time, for example during transport and handlingand/or when transport and handling occurs several weeks after treatment.The solution may be applied at a rate of between 0.005 gallons per tonand 0.2 gallons per ton, preferably 0.02-0.03 gallons per ton.

Other features and advantages of the invention will be apparent from thefollowing specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a schematic of a plurality of fines of a dusting material asit is transferred from a first location to a second location along aconveyor while simultaneously treated with an aqueous liquid solution ofthe present invention and accumulated into a mass of non-dustingmaterial subsequent to application of the aqueous solution wherein theaqueous solution is substantially evenly distributed throughout aninterior portion of the mass of non-dusting material.

DETAILED DESCRIPTION

While this invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

The present invention is directed to an unexpectedly effective methodfor treating a mass of dusting material to suppress the generation ofdust therefrom during handling and storage, the mass of dusting materialhaving, prior to treatment, the propensity to generate dust duringroutine handling. The method comprises applying to the dusting materialan aqueous solution comprising a mixture of soluble cellulose ether, aplasticizer, and one or more surfactants and thoroughly mixing thedusting material with the aqueous solution, thereby reducing oreliminating the ability of the dusting material to generate dust duringroutine handling.

The invention described herein is a significant and unexpectedimprovement in the strength of water-based dust control treatmentsproduced using water-soluble cellulose ethers. The previous work,specifically Roe in the '859 patent, taught the use of water solublecellulose ethers as binders, albeit at higher temperatures than arecontemplated in this application. As discussed above, the addition of aplasticizer would only be expected to weaken a binding agent and thusthe use of a plasticizer would have been viewed as a detriment to thebest achievable binding strength of a dust control formulation. However,contrary to expectations, adding a plasticizer instead actuallystrengthens the particle-to-particle adhesion formed in theseapplications. Water-soluble cellulose ether formulations containingplasticizers and surfactants are found to offer a significantimprovement in strength and reduction of dusting when compared tosimilar formulas which lack plasticizers.

The majority of the present work has been performed on coal. However,one skilled in the art will recognize that this invention is equallyapplicable to a wide range of dusting bulk materials, examples of whichinclude, and are not limited to: taconite, limestone, crushed rock,gravel, sand, gypsum, cement, ash, petroleum and metallurgical coke,wood chips, and a variety of industrial ores.

The present invention relates to the use of water-soluble celluloseethers to bind dust when applied to a variety of materials. In general,water-soluble cellulose ethers are dispersed in water and stirred untilfully hydrated, producing a homogeneous solution. The plasticizer andsurfactant are added at any point during the manufacturing step and thematerial is usually diluted and sprayed onto a flowing mass of dustingmaterial.

The first step, dispersing and hydrating the cellulose ether can beaccomplished in a number of ways as detailed in the “Methocel CelluloseEthers Technical Handbook” available from Dow's web site:(http://www.dow.com/webapps/lit/litorder.asp?filepath=methocel/pdfs/noreg/192-01062.pdf&pdf=true).It was discovered to be particularly convenient to use a powder eductorsuch as the devices offered by Compatible Components (www.cccmix.com) todisperse cellulose ether powders.

The class of cellulose ethers includes methylcellulose, ethyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethylmethylcellulose, hydroxypropyl methylcellulose, and generallyhydroxyalkyl methylcellulose such as those sold by Dow ChemicalCorporation under the trade name METHOCEL®. Methylcellulose wasdiscovered to be very effective in this technology, and particularly themoderate viscosity materials that would form a 4,000 cPs viscositysolution at 2.5 wt. %. At the same time, lower viscosity hydroxypropylmethylcellulose, such as material that will form a 400 cPs solution at2.5 wt. %, can be equally effective if employed at slightly greaterconcentrations. Viscosity for cellulose ethers is generally used todefine different molecular weights. Thus, a 400 cPs methylcellulose willhave a viscosity of 400 cPs at a concentration of 2.5%, and a 4000 cPsmethylcellulose will have a viscosity of 4,000 cPs at a concentration of2.5%. Lower concentrations will have lower viscosities. It wasdiscovered that the strengthening effect of plasticizers does not extendto anionic carboxymethylcellulose.

A number of different plasticizers, including diethylene glycol,propylene glycol, glycerin, triethanolamine, dextrose, andpentaerythritol have been tested, and every indication is that this is ageneral phenomenon of all plasticizers in this application. From aneconomic standpoint, obviously, some of these plasticizers will be morecost effective. In particular, glycerin has been found to be effectiveand abundant in the current market as it is a byproduct from biodieselproduction. As markets change, and particularly as glycerin becomes apreferred chemical feedstock, we expect diethylene glycol and dextroseto remain economically viable alternatives to glycerin.

The use of a cross-linking agent, glyoxal, has been examined in thesesystems, and a further increase in strength for crusts was produced andobserved in this manner. This was expected, and similar improvements tothe strength with other cross-linking systems such as borates orzirconium salt-based cross-link systems would be further expected.

Wetting agents are essential to insure the efficient coverage of thecellulose ether solution onto the dusting material. This area of dustcontrol is well-understood by those of ordinary skill in the art, andsolutions of salts of alkylbenzene sulfonates, dialkyl sulfosuccinates,fatty acid amides, quaternary ammonium compounds, organic phosphateesters, nonionic fatty acid alcohol ethoxylates and mixedethoxylate-propoxylates, as well as synthetic alcohol ethoxylates andmixed ethoxylate-propoxylates have all been used in the past. Commercialpreparations are available from a number of manufacturers, and in thepresent invention materials produced by Benetech, Inc., of Aurora, Ill.were used. The inventors contemplate that cationic, anionic, or nonionicsurfactants are chemically compatible in combination with other aspectsof this invention.

The addition of insoluble reinforcing agents are anticipated to be aseffective in these formulations as they are in non-plasticized celluloseether formulas.

The application rate for the mixture can vary widely. In general, moreis better, but at some point maximum dust control is achieved and addingadditional binding agent has no performance benefit and an economicpenalty. Thus, application rates between 0.005 gallons of theconcentrated nonionic cellulose ether solution per ton and 0.2 gallonsper ton will all generally provide adequate short-term and long-termdust suppression. It was discovered that more effective applicationrates were between 0.01 gallons per ton and 0.05 gallons per ton. Mosteffective application rates were generally in the range of 0.02 gallonsper ton to 0.03 gallons per ton.

As explained above, the formula of the present invention is a method ofusing a solution to reduce airborne dust from a dusting material. Thesolution comprises a non-ionic cellulose ether, a surfactant and water.A plasticizer is added to the liquid solution prior to drying the liquidsolution on the dusting material. The non-ionic cellulose etherpreferably has a viscosity between 3 cPs and 100,000 cPs when measuredat a concentration of 2.5 percent in water, and more preferably between50 cPS and 10,000 cPS, e.g., a hydroxypropyl methylcellulose etherhaving the prescribed viscosity and making up no more than 20 percent byweight of the solution. The plasticizer is preferably glycerin at nomore than 200 percent weight of the non-ionic cellulose ether.

Thus, a typical formula is produced by dispersing 650 lbs of lowviscosity (about 400 cPS for a 2.5% solution) hydroxypropylmethylcellulose in a 4,150 gallon water solution containing 145 lbs ofglycerin and adding approximately 850 gallons of a commercial dustwetting formulation such as BT-205W (supplied by Benetech, Inc. ofAurora, Ill.). The solution is stirred for two hours to insure completehydration of the cellulose ether then applied to a dusting material at arate of 0.03 gallons per ton

EXAMPLES Example 1 Measurement of Strength for Plasticized andNon-Plasticized Cellulose Ether Formulations

To a sample of damp 18 mesh to 60 mesh (1 mm-0.25 mm) sub-bituminouscoal was added a solution of 1.5 wt. % 400 cPs hydroxypropylmethylcellulose (HPMC). The solutions contained 1.0 wt. % commercialcoal wetting solution concentrate (BT-205W supplied by Benetech, Inc.).The solution also contained plasticizers of the indicated composition.The amount added was such that the total mass of the sample wascomprised of 20 wt. % or 25 wt. % of the solution with the remaining 80wt. % or 75 wt. % coal. The samples were mixed and pressed into 30 mmdiameter round plastic forms with a depth of 15 mm. The samples wereheated to 40° C. overnight and in the morning cooled and broken using aforce gauge. The maximum force required (in milliNewtons) to break thesample was divided by the mass of the sample (in grams) to give aspecific strength that was independent of the mass of the sample.Results are shown in Table 1, with the lowest strength measurementsunderlined and the highest strength measurements double underlined. Thecombined results are simply the average of all 26 tests:

TABLE 1 Specific Strengths of Coal-HPMC Articles after Drying 20%Solution 25% Solution Addition Addition Combined Composition (9 Samples)(17 Samples) Results 1.5% HPMC Solution, 1827.1 mN/g 2326.1 mN/g2139.0 mN/g no Plasticizer (15 samples) (24 samples) 1.5% HPMCSolution + 2428.2 mN/g 3604.6 mN/g 3197.4 mN/g 0.5% Pentaerythrytol 1.5%HPMC Solution + 2369.92 mN/g 2756.50 mN/g  2622.7 mN/g 0.5%Triethanolamine 1.5% HPMC Solution + 2205.6 mN/g 2587.2 mN/g 2455.1 mN/g0.5% Glycerin 1.5% HPMC Solution + 2572.9 mN/g 2747.6 mN/g 2687.1 mN/g0.25% Glycerin 1.5% HPMC Solution + 2672.93 mN/g 2915.96 mN/g  2831.8mN/g 0.5% Propylene glycol 1.5% HPMC Solution + 2617.3 mN/g 2912.9 mN/g2810.6 mN/g 0.5% Diethylene Glycol 1.5% HPMC Solution + 2328.2 mN/g2816.7 mN/g 2647.6 mN/g 0.5% Dextrose

As can be seen, in all cases the addition of a plasticizer strengthenedthe articles. The clear implication is that when these solutions areapplied to a substrate, the substrate treated using a cellulose etherand surfactant solution with a plasticizer will more strongly bind thedust particles than one treated with cellulose ether and surfactantsolution without a plasticizer, or simply a cellulose ether solution.

Example 2 Examination of the Effect of Cellulose Ether Chemistry on theStrength of Coal-Dust Binding

To a sample of 18 mesh to 60 mesh (1 mm-0.25 mm) sub-bituminous coal wasadded a solution of 1.5 wt. % of various cellulose ethers. The celluloseethers were produced by Dow and their chemistry and nomenclature arediscussed in the previously cited “Methocel Cellulose Ethers TechnicalHandbook” available from Dow's web site. All cellulose ethers were ofthe same viscosity grade: 4,000 cPs at a 2.5 wt. % solution. Thechemistries ranged from “A” chemistry which was pure methylcellulose,through “E”, “F”, “J”, and “K” chemistries. Of thehydroxypropyl-substituted cellulose ether chemistries it is worth notingthat “F” chemistry has the least amount of hydroxypropyl substitution.The solutions contained approximately 22 wt. % commercial coal wettingsolution concentrate (BT-205W supplied by Benetech, Inc.). The amountadded was such that the total mass of the sample was comprised of 25 wt.% of the solution with the remaining 75 wt. % coal. The samples weremixed and pressed into 30 mm diameter round plastic forms with a depthof 15 mm. The samples were heated to 40° C. overnight and in the morningcooled and broken using a force gauge. The results are detailed in Table2. Each result is the average of nine tests.

TABLE 2 Chemistry A E F J K Breaking force 84 N 32 N 38 N 24 N 20 N

As can be seen, the “A” chemistry, that is, pure methylcellulose,produces a much stronger composite than any of the varioushydroxypropyl-substituted methylcelluloses.

Example 3 Measurement of Strength for Plasticized and Non-PlasticizedSodium Carboxymethylcellulose Ether Formulations

To a sample of dry fresh-ground 18 mesh to 60 mesh (1 mm-0.25 mm)sub-bituminous coal was added a solution of 4.0 wt. % sodiumCarboxymethylcellulose (supplied by Ashland Chemical, Aqualon Division,type 7L). The solutions contained 0.5 wt. % commercial coal wettingsolution concentrate (BT-210WF supplied by Benetech, Inc.). The solutionalso contained plasticizers of the indicated composition. The amountadded was such that the total mass of the sample comprised 25 wt. % ofthe solution with the remaining 75 wt. % coal. The samples were mixedand pressed into 30 mm diameter round plastic forms with a depth of 15mm. The samples were heated to 41° C. overnight and in the morningcooled and broken using a force gauge. The maximum force required (inNewtons) to break the sample was divided by the mass of the sample (ingrams) to give a specific strength that was independent of the mass ofthe sample. Results are shown in table #3, and each number representsthe average of nine samples.

TABLE 3 Test solution Specific Strength 4% 7L CMC 0.5% 210WF 13.10 N/g4% 7L CMC 0.5% 210WF, 0.8% glycerin 12.10 N/g 4% 7L CMC 0.5% 210WF 1.6%glycerin 11.98 N/g 4% 7L CMC 0.5% 210WF 0.8% diethylene glycol 12.38 N/g4% 7L CMC 0.5% 210WF 1.6% diethylene glycol 12.59 N/g

As can be seen, and unlike nonionic cellulose ethers, we found noincrease in strength for articles formed from carboxymethylcellulosewith plasticizers, and possibly a slight decrease in strength. Thehigher strengths compared to the first example are attributed to thehigher concentrations of sodium carboxymethylcellulose compared to HPMCdiscussed in the first example.

General Procedure for Evaluation of Crusts:

To further quantify the advantages of adding a plasticizer todust-suppression formulas we examined the strength of non-compacted coalunder conditions simulating dew, rain, and solar heating where thesuppressant was applied to one surface and allowed to set. For examples4-6, the procedure outlined herein was used to evaluate the strength ofsub-bituminous coal to which the dust suppressant had been applied as abinder.

Sub-bituminous coal was sieved with the fraction less than one inch(25.4 mm) collected. The coal was moistened until visible surfacemoisture was present, roughly matching the surface moisture offresh-mined coal. Three to six kilogram portions of this coal were takenand divided into samples of about 990 grams each. The samples wereplaced and loosely leveled (not compacted) in trays using disposable8.5″ diameter aluminum pie plates. The samples were labeled and treatedat the noted rate with the test solutions. The samples were then allowedto dry overnight and subsequently deionized water was applied at theequivalent of about 1/20'th of an inch (˜1 mm) of rain or heavy dew. Thesamples were again dried overnight and then wet with the equivalent of1/10 inch of rain (2.5 mm) The samples were again allowed to dry andthen heated under heat lamps to between 40° C. and 60° C. for four hoursto simulate the effect of hot sun on the treated coal. Samples werecooled and the coal mass was broken using a force gauge fitted with a9.5 mm blunt rod probe. The maximum force was recorded and the pieceswere weighed to determine the mass of the sample bound. Using thedensity of the coal and the diameter of the sample, the thickness wasthen calculated.

Example 4 Addition of Plasticizer or Surfactant to HPMC

Solutions of 2.5% 400 cPs HPMC and 1.0% BT-205W were treated with either1.0% BT-205W surfactant mixture (A) or 5.00% glycerin (B). The solutionswere applied at an application rate of 0.024 gallons per square foot.Three trays of each solution with coal were prepared and treated as perthe general procedure above to give the following results (Table 4):

TABLE 4 Test Thickness, in Strength, psi Solution A (surfactant) 0.41112 Solution B (plasticizer) 0.49 116

As can be seen, the HPMC solution treated with the plasticizer gavegreater thickness and strength measurements than the HPMC solutioncontaining a surfactant solution.

Example 5 Addition of Plasticizer to HPMC and Surfactant Formula

Solutions of 1.5% 400 cPs HPMC and 1.0% BT-205W (A) and 1.5% 400 cPsHPMC with 1.0% BT-205W and 0.5% glycerin (B) at an application rate of0.035 gallons per square foot were tested. Four trays of each solutionwith coal were prepared and treated as per the general procedure aboveto give the following results (Table 5):

TABLE 5 Test Thickness, in Strength, psi Solution A 0.26 64 Solution B0.27 94

As can be seen, the addition of a plasticizer was effective inincreasing the strength of the coal binding.

Example 6 The Benefit of Adding a Cross-Linker

Solutions of two different cellulose ethers were prepared. Solution Acontained 1.5% 400 cPs HPMC, 0.50% glycerin, and 1.0% BT-205W. SolutionB contained 1.5% 400 cPS HPMC, 0.50% glycerin, 1.0% BT-205W, 0.1%glyoxal solution (40%), and sufficient acetic acid to make the pH<5.Three trays of each solution with coal were prepared and treated as perthe general procedure above at an application rate of 0.04 gallons persquare foot to give the following results (Table 6):

TABLE 6 Test Thickness, in. Strength, psi Solution A 0.80 74 Solution B0.83 93

As can be seen, the addition of a cross-linking agent furtherstrengthens the coal-coal binding.

Example 7 The Benefit of Adding a Plasticizer to Particle Agglomeration

A mixture of 228 grams of 18-60 mesh sub-bituminous coal was thoroughlymixed with 5.85 grams of sub-200 mesh sub-bituminous coal. Twenty gramsamples of the mixture were removed and mixed with water, or a mixtureof 1.5% 400 cPs HPMC and 21. BT-205W (Solution A), or a mixture of 1.5%400 cPs HPMC and 21.% BT-205W and 0.5% glycerin (Solution B) at a rateof 3.3 grams of liquid per 20 grams of sub-bituminous coal mixture.

The samples were gently mixed with a steel spatula and placed in an ovenat 40-41 C.° overnight. The following morning the samples were removedfrom the oven and sieved. The sieving system contained two sieve stacksallowing for two samples to be sieved simultaneously. All resultsrepresent duplicate size determinations (Table 7).

TABLE 7 Retained on Soln. A Soln. B Sieve # Sieve Size Water (noplasticizer) (plasticizer) 18 1,000 microns 0.16% 0.72% 3.57% 60 250microns 95.63% 96.82% 94.93% Sub-60 <250 microns 4.21% 2.46% 1.50% Total100.00% 100.00% 100.00%

As can be seen, the formula with plasticizer dramatically increased theamount of material greater than 1,000 microns when compared to thewater-treated or the cellulose ether and surfactant withoutplasticizer-treated material. The less than 250 micron fraction wasreduced by almost 40 percent simply by adding plasticizer.

From this we can conclude that the addition of a plasticizer to asoluble cellulose ether and surfactant mixture will significantlyincrease the formula's ability to reduce dust by more strongly bindingdust particles to larger particles.

One of ordinary skill in the art would readily appreciate that the fluidsolution of the present invention is used in a full body treatment of adusting material. For example, a dust suppressant of the presentinvention may be sprayed on individual particles of the dusting materialas they are transported on a conveyor. Again, the present inventiontreats individual fines of a dusting material. This is differentiatedfrom a dust suppressant dried to form a crust over the exposed surfaceof a mass or pile of a dusting material, e.g. coal. The mass or pile ofthe dusting material may be within a railcar, a stockyard, or similarlocation. As used in the present application, the phrase “mass or pileof dusting material” refers particularly to any conglomeration ofdusting material lumps or pieces. Thus, a crust formed over an exposedsurface of a mass or pile of a dusting material differs materially froma full body treatment using a dust suppressant in which individualparticles of dusting material are sprayed rather than an exposed surfaceof a mass of dusting material.

With reference to the accompanying drawing, the present invention alsorelates to a method of reducing airborne dust emanating from a pluralityof fines of a dusting material and a method of treating a plurality offines of a dusting material to prevent emanation of dust from thedusting material. Referring to FIG. 1, one or more applicators 14 spraya liquid solution 18 of the present invention onto a stream 20 of adusting material 22 comprising a plurality of fines of the dustingmaterial 22. The dusting material 22 is generally being processed on aconveyor or like apparatus 26 for transferring the dusting material 22from one location to a second location. The solution 18 is generallyapplied to the moving stream of the dusting material 22, either on thetransport apparatus 26 as shown or as the stream is transferred from theapparatus 26, also shown. Mixing between the fines and the solution 18occurs as the stream 20 is transferred, and especially as the stream 20is transferred from the transport apparatus and accumulated at a bulklocation, such as into a mass or pile 30 of the dusting material 22. Inthe mass 30, the aqueous solution 18 is substantially evenly distributedthroughout an interior portion of the mass of the dusting material 22.The solution 18 is dries within the mass which reduces or preventsemanation of airborne fines or dust particles from entering thesurrounding atmosphere.

According to the methods and aspects of the invention, airborne dust isreduced or eliminated during transport and handling of the dustingmaterial, often more than 24 hours after treatment with the solutionaccording to the principles described herein, more preferably more than48 hours after treatment, even more preferably more than seven daysafter treatment, and most preferably more than three weeks aftertreatment. Accordingly, the dusting material 22 may be treated with asolution of the invention as illustrated in FIG. 1 up to several weeksprior to the mass 30 being transported to a different location without asignificant degradation in dusting reduction quality such that airbornedust emanation from the mass 30 remains eliminated or at the very leastgreatly reduced over the same mass 30 of an untreated dusting materialand/or a dusting material treated with an alternative solution.

While the specific embodiments have been illustrated and described,numerous modifications come to mind without significantly departing fromthe spirit of the invention, and the scope of protection is only limitedby the scope of the accompanying Claims.

What is claimed is:
 1. A method of reducing airborne dust emanating froma plurality of fines of a dusting material comprising the steps of:providing a source of an aqueous solution comprising a mixture of awater soluble non-ionic cellulose ether, a plasticizer, and one or moresurfactants, wherein a percentage of the plasticizer in the aqueoussolution is no more than 200 percent by weight of the non-ioniccellulose ether; applying the aqueous solution to a dusting materialcomprising a plurality of fines while the dusting material is beingtransferred from a first location to a second location; and mixing thedusting material with the aqueous solution to coat the plurality offines with the aqueous solution to create a treated dusting material. 2.The method of claim 1 wherein the non-ionic cellulose ether has aviscosity between 3 cPs and 100,000 cPs as measured at a concentrationof 2.5 weight percent in water.
 3. The method of claim 2 wherein thenon-ionic cellulose ether is a methylcellulose ether.
 4. The method ofclaim 2 wherein the plasticizer is glycerin.
 5. The method of claim 2wherein a percentage of the non-ionic cellulose ether is no more than 20percent by weight of the aqueous solution.
 6. The method of claim 2wherein a percentage of the non-ionic cellulose ether is no more than 20percent by weight of the aqueous solution, and a percentage of theplasticizer is no more than 200 percent by the weight of the non-ioniccellulose ether.
 7. The method of claim 2 further comprising the stepof: accumulating the plurality of fines of the treated dusting materialinto a mass of the treated dusting material subsequent to the applyingstep wherein the aqueous solution is distributed throughout an interiorportion of the mass of the treated dusting material.
 8. The method ofclaim 7 wherein the mixing step is performed simultaneously with theaccumulating step.
 9. The method of claim 1 wherein the aqueous solutionfurther comprises a cross-linking agent.
 10. The method of claim 9wherein the cross-linking agent is selected from the group consisting ofglyoxal, borates, and zirconium-salt based cross-linking systems.
 11. Amethod of treating a plurality of fines of a dusting material to preventemanation of dust from the dusting material comprising the steps of:providing an aqueous solution comprising a mixture of soluble non-ioniccellulose ether, a plasticizer, and a surfactant, wherein a percentageof the plasticizer in the aqueous solution is no more than 200 percentby weight of the non-ionic cellulose ether; applying the aqueoussolution to a dusting material comprising a plurality of fines to createa treated dusting material while the dusting material is beingtransferred from a first location to a second location; mixing thedusting material with the aqueous solution to coat the plurality offines with the aqueous solution; and accumulating the plurality of finesof the treated dusting material into a mass of the treated dustingmaterial subsequent to the applying step wherein the aqueous solution isdistributed throughout an interior portion of the mass of the treateddusting material.
 12. The method of claim 11 wherein the non-ioniccellulose ether is an alkyl-substituted cellulose ether.
 13. The methodof claim 11 wherein the plasticizer is selected from the group ofcellulose ether plasticizers consisting of polyols, diols, sugars, fattyacids, fatty acid esters, and polyhydridic alcohols.
 14. The method ofclaim 11 wherein the surfactant is selected from the group consisting ofsolutions of salts of alkylbenzene sulfonates, dialkyl sulfosuccinates,fatty acid amides, quaternary ammonium compounds, organic phosphateesters, ethylene oxide-propylene oxide block copolymers, non-ionic fattyacid alcohol ethoxylates, non-ionic fatty acid alcohol mixedethoxylate-propoxylates, synthetic alcohol ethoxylates, and syntheticalcohol mixed ethoxylate-propoxylates.
 15. The method of claim 11wherein the aqueous solution further comprises a cross-linking agent.16. The method of claim 15 wherein the cross-linking agent is selectedfrom the group consisting of glyoxal, borates, and zirconium-salt basedcross-linking systems.
 17. A method of treating a plurality of fines ofa dusting material to prevent emanation of dust from the dustingmaterial comprising the steps of: providing an aqueous solutioncomprising a mixture of soluble non-ionic cellulose ether, aplasticizer, and a surfactant, wherein a percentage of the plasticizerin the aqueous solution is no more than 200 percent by weight of thenon-ionic cellulose ether; applying the aqueous solution to a dustingmaterial comprising a plurality of fines to create a treated dustingmaterial; transferring the dusting material during the applying stepwherein the dusting material is transferred from a first location to asecond location as the aqueous solution is applied to the plurality offines; mixing the dusting material with the aqueous solution to coat theplurality of fines with the aqueous solution; and accumulating theplurality of fines of the treated dusting material into a mass of thetreated dusting material subsequent to the applying step wherein theaqueous solution is distributed throughout an interior portion of themass of the treated dusting material.
 18. The method of claim 17 whereinthe plasticizer in the solution increases a particle-to-particleadhesion strength in the dusting material when the solution dries whencompared to an untreated dusting material.
 19. The method of claim 17wherein the aqueous solution further comprises a cross-linking agent.20. The method of claim 19 wherein the cross-linking agent is selectedfrom the group consisting of glyoxal, borates, and zirconium-salt basedcross-linking systems.